New composition and method

Abstract

The present invention concerns a composite iron-based powder mix suitable for soft magnetic applications such as inductor cores. The present invention also concerns a method for producing a soft magnetic component and the component produced by the method.

1 . A composite iron-based powder composition comprising core particles, wherein the core particles are a mixture of
 (a) iron alloy particles consisting essentially of 7% to 13% by weight silicon, 4% to 7% by weight aluminium, the balance being iron, and   (b) atomized iron particles,   and wherein said core particles are coated with a first phosphorous containing layer.   
     
     
         2 . Composite iron-based powder according to  claim 1 , wherein the atomized iron particles have a second layer comprising:
 (a) an alkaline silicate combined with a clay mineral containing a phyllosilicate, combined silicon-oxygen tetrahedral layer and hydroxide octahedral layers thereof being electrical neutral, or   (b) a metal organic layer.   
     
     
         3 . Composite iron-based powder according to  claim 2 , wherein the iron alloy particles have a second layer comprising:
 a) an alkaline silicate combined with a clay mineral containing a phyllosilicate, combined silicon-oxygen tetrahedral layer and hydroxide octahedral layers thereof being electrical neutral, or   b) a metal organic layer.   
     
     
         4 . Composite iron-based powder according to  claim 3 , wherein the iron alloy particles and the atomized iron particles have the same second layer. 
     
     
         5 . A composite iron-based powder composition according to  claim 2 , wherein the second layer comprises kaolin and sodium silicate. 
     
     
         6 . A composite iron-based powder composition according to  claim 1 , further comprising atomized FeSi. 
     
     
         7 . A composite iron-based powder composition according to  claim 1 , wherein the phosphorous containing layer has a thickness between 20 and 300 nm. 
     
     
         8 . A composite iron-based powder according to  claim 1 , wherein the phosphorous coating is provided by contacting the core particles with a phosphorous compound in a solvent and afterwards removing the solvent by drying. 
     
     
         9 . A composite iron-based powder according to  claim 1 , wherein the phosphorous compound is phosphoric acid or ammoniumphosphate. 
     
     
         10 . The composite iron-based powder according to  claim 2 , wherein the content of alkaline silicate is between 0.1-0.9% by weight of the composite iron-based powder. 
     
     
         11 . The composite iron based powder according to  claim 2 , wherein the content of clay is between 0.2-5% by weight of the composite iron-based powder. 
     
     
         12 . A method for producing a compacted and heat treated component, comprising the steps of:
 a) providing a composite iron-based powder according to  claim 1 ,   b) compacting the composite iron-based powder, optionally mixed with a lubricant, in a uniaxial press movement in a die at a compaction pressure between 400 and 1200 Mpa,   c) ejecting the compacted component from the die,   d) heat treating the ejected component in a non-reducing atmosphere at a temperature up to 800° C.   
     
     
         13 . A component produced according to the method described in  claim 12 . 
     
     
         14 . A component according to  claim 13 , said component being an inductor core. 
     
     
         15 . An inductor core according to  claim 14 , having a resistivity, ρ, above 1000 μΩm; a saturation magnetic flux density Bs above 1.1 (T); core loss less than 12 W/kg at a frequency of 20 kHz; induction of 0.05 T; coercivity below 210 A/m; and DC-bias not less than 50% at 4000 A/m. 
     
     
         16 . A composite iron-based powder composition according to  claim 3 , wherein the second layer comprises kaolin and sodium silicate.